the complete genome of Bifidobacterium longum FB1-4

The food safety landscape faces a significant challenge from methicillin-resistant Staphylococcus aureus (MRSA), a virulent and antibiotic-resistant foodborne pathogen. This study investigates the antimicrobial properties and mechanisms of cell-free supernatant (CFS) from Bifidobacterium longum FB1-4 against MRSA. The CFS exhibited robust antibacterial activity, achieving a minimum inhibitory concentration (MIC) of 25% and maintaining a bacterial elimination rate of over 80% for 8 hours at 2x MIC, demonstrating superior sustained bactericidal efficacy compared to vancomycin. In a food matrix, FB1-4 CFS exhibited impressive bactericidal effects against three MRSA strains, leading to elimination rates of 94.64% at 2 hours, 98.02% at 4 hours, 99.90% at 6 hours, and nearly complete eradication (99.99%) by 8 hours. Furthermore, FB1-4 CFS suppressed mecA expression, increased antibiotic susceptibility, and diminished biofilm formation by 70%. Transcriptomic and metabolomic analyses revealed that FB1-4 CFS modulates two-component systems and quorum sensing, leading to reduced virulence factor expression. In vivo studies confirmed a 90% reduction in MRSA colonization in mouse intestines. These findings provide critical insights into how probiotic metabolites inhibit MRSA, underscoring their potential as natural therapeutic agents in food safety.

食品安全领域面临着来自耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus, MRSA）的严峻挑战，该病原菌兼具强毒性与抗生素耐药性，属于食源性致病菌。本研究探究了长双歧杆菌FB1-4（Bifidobacterium longum FB1-4）所产无细胞上清液（cell-free supernatant, CFS）对抗MRSA的抗微生物活性及其作用机制。该无细胞上清液展现出优异的抗菌活性，最低抑菌浓度（minimum inhibitory concentration, MIC）为25%，且在2倍MIC浓度下可维持8小时以上的细菌清除率超80%，相较于万古霉素（vancomycin）体现出更优越的持续杀菌效能。在食品基质中，FB1-4 CFS对三株MRSA均展现出显著的杀菌效果：2小时时细菌清除率达94.64%，4小时为98.02%，6小时升至99.90%，至8小时时几乎实现完全清除（99.99%）。此外，FB1-4 CFS可抑制mecA基因表达、提升抗生素敏感性，并使生物被膜（biofilm）形成量减少70%。转录组学与代谢组学分析显示，FB1-4 CFS可调控双组分系统与群体感应通路，进而降低毒力因子的表达。体内实验证实，该上清液可使小鼠肠道内的MRSA定植量降低90%。本研究结果为益生菌代谢产物抑制MRSA的机制提供了关键见解，凸显了其作为食品安全领域天然治疗制剂的应用潜力。